Filter element

ABSTRACT

A filter element ( 1 ) having at least one inner ( 12 ) and an outer casing body ( 11 ), of which at least one casing body ( 12 ) has a cross section deviating from circularity and which have contact surfaces ( 20, 21 ) facing one another for the contact of essentially all filter folds ( 18   a - 18   f,    18   I - 18   II ) of a pleated filter web ( 10 ), the filter folds ( 18   a - 18   f,    18   I - 18   II ), in terms of fold height (h), being divided into individual groups (I, II) each having several filter folds ( 18   I   , 18   II ) of a common fold height (h max , h min ) alongside one another in sections, is characterized in that between two adjacent filter folds ( 18   a - 18   f,    18   I - 18   II ) of different groups (I, II) are arranged filter folds ( 18   b - 18   e;    18   m ) of at least one further third group (Ill), the filter folds ( 18   b - 18   e,    18   m ) assigned to the third group (III), in the manner of step formation, have a common fold height (ho) which is different from the respective fold height (h max , h min ) of the filter folds ( 18   I   , 18   II ) of the two adjacent neighbouring groups (I, II), and/or, in the manner of curve formation, have different fold heights, which establishes a transition between the fold heights (h max , h min ) of the two adjacent groups (I, II).

The invention relates to a filter element having at least one inner and one outer jacket body, of which at least one jacket body has a cross-sectional shape that deviates from a circular shape, and which have contact faces, which face one another for the contact of essentially all of the filter folds of a pleated filter web, wherein, in terms of the fold height, the filter folds are divided into individual groups, each having a plurality of filter folds that are arranged alongside each other in sections and exhibit a common fold height.

Filter elements of this type are commercially available. Such filter elements are widely used in conjunction with fluid systems of the most diverse type to filter process fluids, hydraulic fluids such as hydraulic oils, liquid fuels and lubricants, for treating liquid media, and the like. In many cases, the fluid systems in which the filter elements are used have only a limited amount of usable space for the installation or attachment of the system parts that contain the respective filter elements in the form of filter cartridges. On the other hand, the filter surface area provided by the filter element has to be large enough to be able to filter the correspondingly large filter flows.

In order to provide a sufficiently large filter surface area, the prior art filter elements, which are readily available on the market, have a filter web that is typically composed of multiple layers of different filter materials and is folded or pleated in a zigzag manner. This filter web is laid around a solid support tube, which is provided with perforations and disposed in the interior of the filter element. During production, the filter web, also referred to as the filter surface area part, is fed through a cutting unit in the longitudinal direction of the web. Then the edge of the filter web is cut to size in said cutting unit, before the web is passed on to a folding machine, in which the zigzag shape or the pleat is formed. Then, in the next phase of the production, the cut-to-size filter web is split into web segments, which are then formed into a tubular body and constitute, in this case, the filter element.

DE 10 2004 026 862 A1 relates to a filter element which can be accommodated in a filter housing for filtering fluids and is configured as a filter cartridge that extends along a longitudinal axis in the form of a body in which an inner fluid space is surrounded by a filter material. In order to separate the inner fluid space from an outer fluid space inside the filter housing, the body of the filter element has a cross section in the shape of an orbiform curve that deviates from a circular shape. A plurality of filter elements in the shape of an orbiform curve are installed in the filter housing in such a positional orientation that they are placed adjacent to the wall of the filter housing with the central region of their outer side, which is curved in the shape of an arc with the larger radius of curvature.

A filter element of the above-described type is known from DE 20 2009 000 969 U1. The filter element known from the prior art has a pleated filter medium and two end plates as well as an outer cross-sectional shape, which deviates from the shape of a circularly round cylinder. The filter medium has folds with variable fold heights, which vary in the manner of steps between a first fold height and a second fold height. The panel air filter element known from DE 20 2009 000 969 U1 has regions with folds of variable height, so that the folds of the same height are arranged alongside each other in sections; and the folds are produced from a single continuous web.

With respect to this state of the art, the object of the present invention is to further improve the ratio of the filter surface area to the required installation space, so that system parts, which are provided for filtering the respective fluids, can be made in an especially space saving manner and at the same time provide the largest filter surface area possible.

This object is achieved by means of a filter element having the features specified in claim 1 in its entirety. A filter element according to the invention is characterized in that the filter folds of at least one additional third group are arranged between two adjacent filter folds of different groups; that the filter folds assigned to the third group in the manner of a step formation have a common fold height, which is different from the respective fold height of the filter folds of the two adjacent adjoining groups, and/or have in the manner of a curve formation mutually different fold heights, which produce a transition between the fold heights of the two adjacent groups. Advantageous embodiments of the filter element according to the invention are the subject matter of the dependent claims.

Due to the fact that at least one portion of the filter folds has a mutually different fold height and that at least one contact face has a shape that deviates from a cylindrical type of construction, an optimized, in particular, enlarged, filter surface area is made available while simultaneously enhancing the utilization of the installation space. In particular, the filter element according to the invention can be arranged in non-symmetrical design space geometries such that the largest possible filter surface area is made available. The jacket bodies are configured advantageously so as to match the installation space. According to the invention, the filter folds are configured and arranged in such a way that the distance, in other words, the free space, between the inner and the outer jacket body is maximally used. In other words, the filter folds extend along the respectively available filter space between the outer and the inner jacket body.

Typically, the filter folds are arranged in direct succession and/or such that they extend parallel to each other. In this embodiment of the filter element according to the invention, the filter space is used in the best possible way for forming the filter surface area. The filter folds usually extend perpendicular to the direction of extension of the typically rectangular filter web. In order to form the filter element, the rectangular filter web is closed in the form of a jacket. In this case, the filter web is connected preferably at its filter web ends so as to form a tubular filter jacket. The fold geometries as well as the geometry of the filter element are variably adjustable and can be chosen as a function of the respective installation space, the inflow conditions, in particular the load per unit area, and/or the filter size. For reasons of expediency, the filter web is composed of several, at least two, layers of filter material.

Preferably, the folds that are adjacently juxtapositioned in sections and are assigned to the third group have the same fold height or rather the same fold depth, so that homogeneous filtration properties are achieved in the respective surface region. As an alternative, the fold height of the corresponding filter folds assigned to the third group can be designed so as to follow a wave-shaped and/or sine-shaped progression. The wave shape or sine shape is configured preferably only on the outside or the inside of the filter web or more specifically on the respective jacket body. However, this wave or sine shape can also be provided on both sides. By varying the inner and/or outer cross sections of the inflow and outflow, the flow conditions are optimized during the inflow or outflow of the fluid to be filtered. The result of this is a reduction in the k value or more specifically the pressure loss in the system. Filter folds exhibiting a smaller fold height are usually mechanically more stable and lead to a stabilization or rather increase in the mechanical stability of the entire filter surface area part. Filter folds having a larger fold height have a larger filter surface area, because a larger web surface area is required to form this larger height; and, as a result, these filter folds have a higher contamination retention capacity. In this way, the particulate removal efficiency, that is, the beta values are improved. Owing to the combination of filter folds having a smaller and larger fold height, both a mechanical stabilization and an improved contamination retention capacity or more specifically an improved particulate removal efficiency are achieved simultaneously.

In a preferred embodiment of the filter element according to the invention, the shape of the cross section of the inner and/or the outer jacket body is provided by a convex polygon, in particular a Reuleaux polygon or more specifically an orbiform curve. The characteristic property of a Reuleaux polygon is that it has a constant width, independently of the direction in which this width is measured. A filter element that is designed in this way can be installed into an installation space having a surface area cross section that is as large as possible. The shape of a Reuleaux polygon or more specifically an orbiform curve that deviates from a circular shape makes it possible to house a larger filter surface area in a given installation space than would be possible in the case of a filter element having a cross section in the shape of a circular cylinder. The shape of an orbiform curve that deviates from a circular shape makes it possible to integrate the filter element in a space saving way in conformity with the given limits of the installation space so that a larger periphery of the filter element and, thus, a larger filtering surface area are available in the given installation space than would be possible if a cylindrical filter element were to be installed at the same installation site.

The filter folds are arranged in an advantageous manner along the filter web following a periodic course, preferably having a period of 15 to 20 filter folds. This offers the advantage of spatially homogeneous properties of the filter element with respect to shape and pressure stability, filtration efficiency, and/or inflow and outflow characteristics. The minimum and maximum fold height or rather fold depth is chosen as a function of the intended use and the installation space. Advantageously, the transition from the minimum to the maximum fold height is arranged so as to extend over the course of four to five folds, which are arranged or rather lie alongside each other and are assigned to the third group, in order to avoid sharp transitions between the first and the second group. It is even more characteristic that the filter fold height of at least a first and at least a second group of filter folds has the same height in each instance; and, hence, the same fold height occurs multiple times in a distributed manner over the periphery of the filter element. Independently of the number of possible filter folds, one such period of filter folds that is adapted to the available filter space is always chosen in each case. It goes without saying that such an adaptation also applies to the number of folds, arranged alongside each other, in order to avoid sharp transitions.

Preferably, the filter folds are configured so as to have the same shape and/or are evenly spaced. In addition to the ease with which the filter element can be fabricated, homogeneous properties of the filter element are achieved. In particular, the load per unit area can be made homogeneous on the inflow side of the filter element. Furthermore, it is advantageous that the filter folds are configured in such a way that their cross section has at least partially a zigzag shape and/or sickle shape. The production of a filter fold having a zigzag shape is very simple, in terms of fold technology. Even a design as a trapezoid fold is conceivable and advantageous. Folds that are pleated in the shape of a star are especially advantageous with respect to the inflow of the fluid to be cleaned. Filter folds that are designed in the shape of a wave can be configured preferably as so-called sine-shaped folds. Folds designed in the shape of a sickle are characterized in that their free ends are arranged so as to be offset with respect to the opposite end of the filter web. In such an embodiment, an even larger filter surface area is made available in the installation space.

Additional advantages and features of the invention will become apparent from the figures and the following description of the drawings. The features shown in the figures are purely schematic drawings and not drawn to scale. Referring to the drawings:

FIG. 1 a is a top view of a filter element according to the state of the art;

FIG. 1 b is a side view of a disassembled filter web according to the state of the art;

FIG. 2 a is a top view of a filter element according to the invention;

FIG. 2 b is a side view of the disassembled filter web from FIG. 2 a;

FIG. 3 a is a side view of an additional filter web of an additional inventive filter element in the disassembled state;

FIG. 3 b is a perspective view of the additional filter web from FIG. 3 a;

FIG. 4 is a side view of an additional filter web of an additional filter element according to the invention;

FIG. 5 a is a top view of the filter housing, which is shown in the partially opened state with an inventive filter element arranged in said filter housing;

FIG. 5 b is a perspective view of the filter housing from FIG. 4 a in a state in which it is partially cut open;

FIG. 6 a-FIG. 6 d is in each instance a schematic drawing of a Reuleaux polygon.

FIG. 1 a shows a filter element 1 according to the state of the art with a folded filter web 10, which is formed into a round tubular body and is laid around a fluid permeable inner jacket body 12, designed as a support tube. Lying on the outside is an outer jacket body 11, indicated by a dashed line. Each of the two jacket bodies 11, 12 has a cross section in the shape of a circle. The circular cross-sectional shape of the outer and inner jacket body 11, 12 has a common center point M. In other words, the inner jacket body 12 and the outer jacket body 11 are arranged concentrically to each other. During the filtration operation, the filter element 1 or more specifically its filter folds 18 a-18 c are traversed by flow from the outside to the inside, that is, in the direction of the center point M. A connecting region 14 of the filter web 10 is formed on the filter web ends 16 a, 16 b, which form the closure of the tubular body. The connecting region 14 can be made by welding or gluing the longitudinal edges, which are arranged alongside each other at the ends 16 a, 16 b of the filter web.

In the pleated filter web 10, the filter folds 18 a-18 c, which have substantially the same shape, have in each instance the same filter height h and rest in each instance against both an outer contact face 20, which is defined by the outer jacket body 11, and against an inner contact face 21, which is defined by an inner jacket body 12. Associated with this is also the fact that the filter height h of the filter folds 18 a-18 c corresponds to at least the radial distance between the inner 21 and the outer contact face 20 or rather between the inner 12 and the outer jacket body 11.

FIG. 1 b is a side view of a filter web 10 of an additional filter element (not illustrated) according to the state of the art. The filter folds 18 _(II), 18 _(II), which are arranged alongside each other along the filter web 10, are divided into two groups I, II. The filter folds 18 _(I) of the first group I have a first fold height h₁ and are arranged in the middle section 26′ of the filter web 10 in such a way that they are arranged alongside each other. The filter folds 18 _(II) of the second group II have a second fold height h₂ and are arranged in the left section 26 and in the right section 26″ of the filter web 10 in such a way that they are arranged alongside each other in each instance. The second fold height h₂ is smaller than the first fold height h₁, so that a sharp transition between the filter folds 18 _(I), 18 _(II), which are arranged so as to be adjacent to each other at the respective transitions, is formed at the transition from the left 26 to the middle section 26′ and from the middle section 26′ to the right section 26″. The left 26 and/or the right section 26″ of the filter web 10 can be followed by additional filter folds 18 _(I), 18 _(II) of the two groups I, II with a fold height that changes in the manner of a step between the first h₁ and the second fold height h₂.

FIGS. 2 a and 2 b show a filter element 1 according to the invention, comprising a filter web 10 with filter folds 18 a-18 f, 18 _(I)-18 _(III), which define a circular cross-sectional shape of the outer jacket body 11 and a cross-sectional shape of the inner jacket body 12 that deviates from the shape of a circle, because of the different filter heights h_(min), h_(max). The filter folds 18 a-18 f, 18 _(I)-18 _(III) are arranged in direct succession along a direction of extension 24 of the filter web 10 and have a constant outer fold distance b. The inner fold distance along the inner jacket body 12 varies between the minimum inner fold distance a′ and a maximum inner fold distance a. The filter folds 18 f, 18 _(I) of the first group I with a maximum fold height h_(max) exhibit the maximum inner fold distance a; and the filter folds 18 a, 18 _(II) of the second group II with a minimum fold height h_(min) exhibit the minimum inner fold distance a′. All of the filter peaks defined by the filter folds 18 a-18 f, 18 _(I)-18 _(II), protrude internally and externally and rest against a contact face 20, 21 on the respective jacket body 11, 12, with the outer contact face 20 having a cylindrical shape, and the inner contact face 21 having a shape that deviates from the cylindrical shape.

The filter folds 18 a-18 f, 18 _(I)-18 _(III) are arranged and configured periodically with a period f along the direction of extension 24 of the filter web 10. In the present example, the period f comprises 17 filter folds. In a first section 26 a, comprising four filter folds 18 b-18 e of the third group III, the fold height decreases continuously from a maximum value h_(max) of the first group I or more specifically the filter folds 18 f, 18 _(I) corresponding to the fold height h_(max) to the minimum value h_(min) of the second group II or more specifically the fold height h_(min) of the corresponding filter folds 18 a, 18 _(II). The adjoining second section 26 _(min) has five filter folds 18 a, 18 _(II) of the second group II with a minimum fold height h_(min). This second section is followed by a third section 26 b with four filter folds 18 _(III) of the third group III having a filter height that increases continuously from a minimum value h_(min) to a maximum value h_(max) following a linear course. The maximum value h_(max) of the fold height is exhibited in turn by the four filter folds 18 _(I) of the first group I in a fourth section 26 _(max).

The illustrated and described parameters, the filter height h having a minimum value h_(min) and a maximum value h_(max), the period f, the minimum inner fold distance a′, the maximum inner fold distance a as well as the outer fold distance b and the total number of filter folds 18 a-18 f, 18 _(I)-18 _(III) can be variably adjusted and optimized as a function of the respective application of the filter element 1 and to match the installation space. FIG. 2 a shows very clearly that the filter element 1 can be inserted into a conventional cylindrical installation space, because the design according to the invention is visible only on the inner jacket body 12, which is formed to match.

FIGS. 3 a and 3 b show an additional filter web 10, which is folded in the form of pleats, with said filter web having filter folds 18 a-18 f, which vary between a minimum filter height h_(min) and a maximum filter height h_(max). These filter folds are arranged to lie closely alongside each other and are divided into three groups I, II, III. In the direction of extension 24 from the first end 16 a of the filter web to the second end 16 b of the filter web, the filter height of the filter folds 18 _(I)-18,_(III) varies with the period f comprising four filter folds 18 _(III) of the third group III with a decreasing fold height in the first section 26 a, five filter folds 18 _(II) of the second group II with a minimum fold height h_(min) in the second section 26 _(min), four filter folds 18 _(III) of the third group III with an increasing fold height in the third section 26 b, and four filter folds 18 _(I) of the first group I with a maximum filter height h_(max) in the fourth section 26 _(max). It is very clear from FIG. 3 b that in order to avoid sharp transitions, the transition from the minimum fold height h_(min) to the maximum fold height h_(max) is designed so as to be “soft,” in other words, in a flowing or continuous manner with a slight decrease or increase.

The aforementioned exemplary embodiments involve only preferred alternative solutions that can also be modified, in particular, with respect to the number of folds and the fold height. In addition to the said geometries in the form of a zigzag or sickle shape, etc., so-called loop folds can also be used in the fold geometry; and moreover, the fold geometry can also be freely specified and designed as a function of the intended application.

FIG. 4 is a side view of an additional filter web of an additional filter surface element, which is not shown in its entirety. The drawing from FIG. 4 corresponds for the most part to the drawing from FIG. 2 b and differs from FIG. 2 b in that the filter folds 18 b-18 e, 18 _(III) of the third group III have both the same third fold height hp as well as altogether this fold height hp in the respective section 26 a, 26 b of the filter web 10. It is very clear from FIG. 4 that the third fold height h_(D) of the filter folds 18 b-18 e, 18 _(III) assigned to the third group III represents the average value of the first fold height h_(max) of the filter folds 18 f, 18 _(I) assigned to the first group I and the second filter fold height h_(min) of the filter folds 18 a, 18 _(II) assigned to the second group II.

However, it is also conceivable that in an embodiment which is not shown, the filter folds 18 b-18 e in the left section 26 a have a fold height that [sic] from the fold height of the filter folds 18 _(III) of the third group III in the right section 26 b. Furthermore, it is possible to provide a filter web 10 with a transition (shown in FIG. 2 b) between the first fold height h_(max) and the second fold height h_(min) that is combined with an arrangement of the filter folds 18 b-18 e, 18 _(III) in the respective section 26 a, 26 b such that this arrangement of said filter folds is in the manner of steps in sections as shown in FIG. 4. In addition, the filter folds 18 b-18 f, 18 _(III) of the third group III can fall below or exceed the first fold height h_(max) and/or the second fold height h_(min) in the respective section 26 a, 26.

FIGS. 5 a and 5 b show a filter housing 30, into which the filter element 1 with the filter web 10 according to FIGS. 2 a and 2 b is inserted. Connected to a head part 32 of the filter housing 30 is a cylindrical installation space 34, into which the filter element 1 with the tubular outer jacket body 11 is inserted. Connected to the inner jacket body 12 (not illustrated) is a hold-down device 36, designed correspondingly in the shape of a Reuleaux polygon, on the head side. The hold-down device 36 is traversed by the flow of a hydraulic medium and is introduced in a positive locking manner into the inner contour of the corresponding element holder. The edge of the hold-down device 36 absorbs the axial forces by way of the protrusions in the element holder. In the illustrated example, the hold-down device 36 is designed for a flow direction from the inside to the outside, as shown with the arrows 50 _(E), 50 _(F), 50. The head part 32 has holes 38 a-38 d as the handling and/or fastening aid as well as an inlet 40 and an outlet 42 for the fluid that is to be cleaned or that has been cleaned. An additional outlet 46 for a return line 50 _(R) is arranged on the end of the filter housing 30 that is situated opposite the head part 32. This additional outlet is also provided with a back pressure valve 48. The filter element 1 can be installed, like a conventional filter part, in the filter housing 30, but when such a filter is running, a larger effective filter surface area with improved stability properties is made available.

FIGS. 6 a-6 d show Reuleaux polygons or more specifically orbiform curves, of which the contour line is marked with the reference numeral 2. In general, a Reuleaux polygon or also a convex polygon has an odd number of corners and consists of nothing but arcs having the same radius. Since the center point of each arc has to lie in the exactly opposite corner 5, 7, 9 of the polygon, the Reuleaux polygon is based on a star polygon 3 (not necessarily regular) with sides of equal length. A Reuleaux triangle, shown in FIG. 6 a, is made of an equilateral triangle 3 by replacing its edges with arcs with the radius equal to the edge length and with the center point in the opposite corner point. The characteristic property of a Reuleaux polygon is that it has a constant width b, independently of the direction in which it is measured.

The orbiform curve shown in FIG. 6 d is based on an equilateral triangle 3 with corner points 5, 7, and 9, with each corner point 5, 7, 9 being a center point of a circle with a radius r₁ and an arc with the radius r₂. These two radii are shown only starting from the corner point 5 in FIG. 6 d. The size of the radius r₂ is chosen in proportion to the radius r₁ in such a way that the corresponding arc is tangential to the circle with the radius r₁ and, in this way, produces the closed contour line, designated as 1 in FIG. 6 d. The diameter d₁ of the orbiform curve formed in this way corresponds to the sum of the radii r₁ and r₂. The periphery of the orbiform curve, that is, the length of the contour line 2, is as large as the periphery of a circle with the diameter d₁. 

1. A filter element (1) having at least one inner (12) and one outer jacket body (11), of which at least one jacket body (12) has a cross-sectional shape that deviates from a circular shape, and which have contact faces (20, 21), which face one another for the contact of essentially all of the filter folds (18 a-1 8 f, 18I-18III) of a pleated filter web (10), wherein, in terms of the fold height (h), the filter folds (18 a-18 f, 18I-18III) are divided into individual groups (I, II), each having a plurality of filter folds (18I-18II) that are arranged alongside each other in sections and exhibit a common fold height (hmax, hmin), characterized in that the filter folds (18 b-18 e, 18III) of at least one additional third group. (III) are arranged between two adjacent filter folds (18 f, 18 a; 18II, 18I) of different groups (I, II); that the filter folds (18 b-18 e, 18III), assigned to the third group (III), in the manner of a step formation have a common fold height (hD), which is different from the respective fold height (hmax, hmin) of the filter folds (18I, 18II) of the two adjacent adjoining groups (I, II), and/or in the manner of a curve formation have mutually different fold heights, which produce a transition between the fold heights (hmax, hmin) of the two adjacent groups (I, II).
 2. The filter element according to claim 1, characterized in that the fold height of the filter folds (18 b-18 e, 18III) assigned to the third group (III) produces a continuous transition between the fold heights (hmax, hmin) of the respective adjacent groups (I, II).
 3. The filter element according to claim 2, characterized in that the respective transition is configured in the shape of a wave and/or sine.
 4. The filter element according to claim 1, characterized in that the adjacently juxtapositioned filter folds (18 f, 18I) of the first group (I) with a first fold height (hmax) and the adjacently juxtapositioned filter folds (18 a, 18II) of the second group (II) with a second fold height (hmin) are arranged in alternating sequence along the filter web (10), and that between these filter folds of the first group and the filter folds of the second group there are arranged the adjacently juxtapositioned filter folds (18 b-18 e, 18III) of the third group (III).
 5. The filter element according to claim 4, characterized in that the fold height along the filter folds (18 b-18 e, 18III) of the third group (III) undergoes transition in alternation from the first filter height (hmax) to the second filter height (hmin) and from the second filter height (hmin) to the first filter height (hmax).
 6. The filter element according to claim 1, characterized in that all of the filter folds (18 b-18 e, 18III) of the third group (III) have the same third filter height (hD).
 7. The filter element according to claims 4, characterized in that the third filter height (hD) corresponds to the average value of the first filter height (hmax) and the second filter height (hmin).
 8. The filter element according to claim 1, characterized in that the filter folds (18 a-18 f, 18I-18III) of at least one group (I-III) are arranged in equal number along the filter web (10) in such a way that they lie alongside each other in sections.
 9. The filter element according to claim 1, characterized in that the filter folds (18 a-18 f, 18I-18III), following a periodic course along the filter web (10), are arranged preferably with a period (f) of 15 to 20 filter folds.
 10. The filter element according to claim 1, characterized in that the inner jacket body (12) has a cross-sectional shape that is provided by a convex polygon.
 11. The filter element according to claim 1, characterized in that the outer jacket body (11) has a cross-sectional shape that is provided by a convex polygon.
 12. The filter element according to claim 10, characterized in that the convex polygon is a Reuleaux polygon.
 13. The filter element according to claim 1, characterized in that the cross section of the filter folds (18 a-18 f, 18I-18III) is configured at least partially in the shape of a zigzag, wave, and/or sickle.
 14. The filter element according to claim 1, characterized in that the filter web (10) is closed and connected at its filter web ends (16 a, 16 b) in a connecting region (14) to the filter element (1). 